Photo-voltaic power generating means and methods

Abstract

A photo-voltaic power cell based on a photoelectric semiconductor compound and the method of using and making the same. The semiconductor compound in the photo-voltaic power cell of the present invention can be electrolytically formed at a cathode in an electrolytic solution by causing discharge or decomposition of ions or molecules of a non-metallic component with deposition of the non-metallic component on the cathode and simultaneously providing ions of a metal component which discharge and combine with the non-metallic component at the cathode thereby forming the semiconductor compound film material thereon. By stoichiometrically adjusting the amounts of the components, or otherwise by introducing dopants into the desired amounts, an N-type layer can be formed and thereafter a P-type layer can be formed with a junction therebetween. The invention is effective in producing homojunction semiconductor materials and heterojunction semiconductor materials. The present invention also provides a method of using three electrodes in order to form the semiconductor compound material on one of these electrodes. Various examples are given for manufacturing different photo-voltaic cells in accordance with the present invention.

What is claimed is: 
     
       1. A method of preparing a photo-voltaic power generating cell comprising: depositing electrochemically on a suitably prepared metal electrode adapted to form a Schottky barrier a coating of a semiconductor compound from an electrolytic bath including the components of said semiconductor compound, said compound being capable of forming a Schottky barrier with said electrode, being transmissive to light radiation and being capable of forming electron-hole pairs upon being irradiated with photons, said components being formed of at least one of the metal elements of Class IIB and non-metal elements of Class VIA of the Periodic Table of Elements.   
     
     
       2. A method as defined in claim 1 wherein said metal electrode is nickel and said semiconductor compound is cadmium sulfide. 
     
     
       3. In a process for depositing a photo-voltaic cell on an electrically conductive semiconductive substrate of a first conductivity type, the steps of: immersing the substrate into an electrolytic bath including an acid solution of cadmium sulfate;   providing an anode having at least a surface layer of tellurium;   applying a voltage between the anode and the substrate forming a cathode, the voltage being negative between the cathode and a calomel reference electrode; and   continuing the plating process until a first thin polycrystalline cadmium telluride layer of said first conductivity type is deposited.   
     
     
       4. In the process defined in claim 3 wherein the substrate is of the n-type and consists of indium tin oxide, and wherein the first conductivity type is the n-type. 
     
     
       5. In the process defined in claim 4 wherein the electrolytic bath includes an n-type donor impurity for codeposition with the n-type cadmium telluride. 
     
     
       6. In the process defined in claim 5 wherein the n-type donor impurity consists of indium sulfate. 
     
     
       7. In the process defined in claim 4 which includes the additional steps of: removing the n-type cadmium telluride layer from the influence of the electric voltage whereby a thin p-type layer is formed;   subjecting the thus formed p-type layer to the influence of a p-type acceptor in the electrolytic bath without applying a voltage thereto; and   electroplating a thin tellurium layer onto said p-type layer from an electrolyte including sodium sulfate without any doping impurities by applying a negative voltage for a time sufficient to create a tellurium layer having a predetermined thickness at an acid pH.   
     
     
       8. In the process defined in claim 7 wherein the p-type acceptor for the formation of the p-type layer consists of arsenic pentoxide. 
     
     
       9. In the process defined in claim 3 wherein the substrate is of the p-type and consists of antimony doped tin oxide, and wherein the first conductivity type is the p-type. 
     
     
       10. In the process defined in claim 9 wherein the electrolytic bath includes a p-type acceptor impurity for codeposition with the p-type cadmium telluride. 
     
     
       11. In the process defined in claim 3 which includes the following additional steps: providing an additional electrolyte including cadmium sulfate and an active impurity of the opposite conductivity type;   immersing the substrate and the first cadmium telluride layer in the additional electrolyte; and   applying a negative voltage with respect to a calomel reference electrode between the cathode and anode, the applied voltage being different from that utilized for depositing the first cadmium telluride layer, thereby to deposit a second thin polycrystalline cadmium telluride layer of the opposite conductivity type, whereby an n-p junction is formed between the first and second cadmium telluride layers to provide a homojunction device.   
     
     
       12. In the process defined in claim 11 wherein the substrate is of the n-type and consists of indium tin oxide and wherein the first conductivity type is the n-type, and wherein the additional electrolyte includes a p-type acceptor impurity and wherein the second cadmium telluride layer is of the p-type. 
     
     
       13. In the process defined in claim 12 wherein the plating voltage for the first cadmium telluride layer between the cathode and the calomel reference electrode is more negative than that applied between the cathode and the calomel reference electrode for the second cadmium telluride layer, whereby more tellurium and less cadmium is deposited for the second layer than for the first layer. 
     
     
       14. The process as defined in claim 12 wherein the p-type acceptor impurity consists of arsenic pentoxide. 
     
     
       15. The process of manufacturing an n-p heterojunction photo-voltaic device utilizing a semiconductive substrate of a first conductivity type, comprising the steps of: immersing the substrate into an electrolyte comprising cadmium sulfate at an acid pH;   providing an anode having at least a tellurium coating;   applying a voltage between the cathode formed by the substrate and the anode, the voltage being negative between the cathode and a calomel reference electrode so as to deposit an opposite conductivity type thin polycrystalline cadmium telluride layer; and   continuing the plating until the layer has a predetermined thickness, whereby an n-p heterojunction is provided between the substrate of a first conductivity type and the plated cadmium tellurium layer of the opposite conductivity type.   
     
     
       16. The process defined in claim 15 wherein the substrate is of the n-type and consists of indium tin oxide and wherein the cadmium telluride layer is of the p-type and is obtained by depositing relatively more tellurium than cadmium. 
     
     
       17. The process defined in claim 16 wherein the electrolyte additionally contains a p-type acceptor impurity for codeposition with the cadmium telluride layer. 
     
     
       18. The process defined in claim 17 wherein said p-type acceptor impurity consists of arsenic pentoxide. 
     
     
       19. The process defined in claim 16 wherein the negative deposition voltage between the cathode and the calomel reference electrode is so selected with respect to the pH, that a p-type layer of cadmium telluride is formed having more telluride than cadmium. 
     
     
       20. The process defined in claim 15 wherein the substrate is of the p-type and consists of antimony doped tin oxide, and wherein the opposite conductivity type is the n-type, the n-type cadmium telluride layer being formed by applying a negative deposition voltage between the cathode and the calomel reference electrode so selected that an n-type cadmium telluride layer is formed having less telluride than cadmium. 
     
     
       21. The process defined in claim 20 wherein the electrolyte additionally includes an n-type donor impurity. 
     
     
       22. The process defined in claim 21 wherein the n-type donor impurity consists of indium sulfate. 
     
     
       23. A process for manufacturing a Schottky barrier photo-voltaic device comprising the steps of: immersing a metal substrate into an electrolytic bath including cadmium sulfate and serving as a cathode;   providing an anode in the bath having at least an outer coating of tellurium;   maintaining the electrolytic bath at an acid pH; and   applying a voltage between the cathode and anode, a negative voltage being measured between the cathode and a calomel reference electrode, the voltage being so selected with respect to the pH that the deposited cadmium telluride consists of a predetermined ratio of cadmium to tellurium to deposit a predetermined conductivity type layer, the deposition being continued until a thin polycrystalline cadmium telluride layer of predetermined thickness is deposited, said metal substrate being capable of forming a Schottky barrier with the deposited cadmium telluride.   
     
     
       24. The process as defined in claim 23 wherein the cadmium telluride layer is of the n-type and is obtained by deposition more cadmium than tellurium. 
     
     
       25. The process as defined in claim 24 wherein an n-type donor impurity is introduced into the electrolytic bath for codeposition with the cadmium telluride. 
     
     
       26. The process defined in claim 25 wherein the n-type donor impurity consists of indium sulfate. 
     
     
       27. The process defined in claim 23 wherein the deposited cadmium telluride layer is of the p-type and consists of less cadmium than tellurium. 
     
     
       28. The process defined in claim 27 wherein a p-type acceptor impurity is introduced into the electrolytic bath for codeposition with the cadmium telluride. 
     
     
       29. The process defined in claim 28 wherein the p-type acceptor impurity consists of arsenic pentoxide. 
     
     
       30. The process for forming a photo-voltaic cell on an electrically conductive n-type semiconductive substrate consisting of indium tin oxide, the process comprising the steps of: immersing the substrate into an electrolytic bath including an acid solution of cadmium sulfate;   providing an anode having at least a surface layer of tellurium;   applying a plating voltage between the anode and the substrate forming the cathode, the voltage being negative between the cathode and a calomel reference electrode;   continuing the plating process until a thin polycrystalline cadmium telluride layer of n-type conductivity is deposited;   immersing the n-type cadmium telluride layer into an electrolytic bath including an acid solution of cadmium sulfate and sodium sulfate;   converting the surface of the cadmium telluride layer into a p-type cadmium telluride layer; and   electroplating a thin tellurium layer onto said p-type cadmium telluride layer for a predetermined period of time to create a tellurium layer of predetermined thickness.   
     
     
       31. The process defined in claim 30 wherein a p-type acceptor impurity is added to the electrolytic bath for plating the p-type cadmium telluride layer. 
     
     
       32. The process defined in claim 31 wherein the p-type acceptor impurity consists of arsenic pentoxide.